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A javascript library for building user interfaces

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Helielson @hyetho @helielson

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Topics What is React? Components SEO Performance Testing Community Who uses

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What's the best way to structure javascript applications?

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There are a lot of javascript frameworks

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Agility.js AngularJS Backbone.js CanJS Derby Dojo Ember.js Firebase + AngularJS Flight jQuery KnockoutJS Knockback.js Maria Meteor Polymer React SocketStream Vanilla JS YUI todomvc.com

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Most of them... Observable Objects Mutation -> Update

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What do we need? Re-render the entire component

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How?

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Re-rendering the DOM on each update is very expensive

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On each update - builds a new virtual DOM subtree - diffs it with the old one - computes the minimal set of DOM mutations and put them in a queue - batch executes all updates

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But, what's react?

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Is it a template language like handlebars.js?

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Nooooooooooo! "To set the record straight: React components are far more powerful than Angular templates; they should be compared with Angular’s directives instead. [Directives are Angular's way of creating custom elements]." Pete Hunt quora.com/Pete-Hunt/Posts/Facebooks-React-vs-AngularJS-A-Closer-Look

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return React.DOM.div( null, "Hello ", this.props.name); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.js

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return React.DOM.div( null, "Hello ", this.props.name); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.js

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return React.DOM.div( null, "Hello ", this.props.name); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.js

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return React.DOM.div( null, "Hello ", this.props.name); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.js

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return React.DOM.div( null, "Hello ", this.props.name); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.js

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var React = require('React'); var HelloMessage = React.createClass({ render: function() { return (
Hello {this.props.name}
); } }); React.renderComponent( HelloMessage({name: "John"}), mountNode); my-button.jsx

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Components "A highly cohesive building block for UIs loosely coupled with other components" Pete Hunt

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Components "Reusable API that encapsulate a bunch of different stuff" Tom Occhino

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- It's the markup - It's the javascript - It's the behavior's function It's more than a template

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The render function render: function() { }

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var MyButton = React.createClass({ render: function() { return ( {this.props.text} ); } });

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var MyButton = React.createClass({ render: function() { return ( {this.props.text} ); } });

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The state

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var Timer = React.createClass({ });

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var Timer = React.createClass({ getInitialState: function() { return {secondsElapsed: 0}; }, render: function() { } });

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var Timer = React.createClass({ getInitialState: function() { return {secondsElapsed: 0}; }, render: function() { this.state.secondsElapsed; // 0 } });

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var Timer = React.createClass({ tick: function() { var current = this.state.secoundsElapsed; this.setState({ secondsElapsed: current + 1 }); } });

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var Timer = React.createClass({ componentDidMount: function() { this.interval = setInterval( this.tick, 1000); }, componentWillUnmount: function() { clearInterval(this.interval); } });

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var Timer = React.createClass({ getInitialState: function() {}, tick: function() {}, componentDidMount: function() {}, componentWillUnmount: function() {}, render: function() {} });

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Lifecycle functions componentDidMount: function() {}, componentWillmount: function() {}, componentWillUnmount: function() {}, componentWillReceiveProps: function() {}, componentComponentUpdate: function() {}, componentWillUpdate: function() {}, componentDidUpdate: function() {},

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Composable Components Inheritance

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var SetIntervalMixin = { componentWillMount: function() { this.intervals = []; }, setInterval: function() { this.intervals.push( setInterval.apply(null, arguments)); }, componentWillUnmount: function() { this.intervals.map(clearInterval); } };

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var Timer = React.createClass({ mixins: [setIntervalMixin], ... });

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SEO

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string renderComponentToString( ReactComponent component);

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And the best part of it is

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var html = React.renderComponentToString( HelloMessage({name: "John"})); Server Client {{html}} React.renderComponent( HelloMessage({name: "John"}), mountNode);

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var html = React.renderComponentToString( HelloMessage({name: "John"})); Server Client {{html}} React.renderComponent( HelloMessage({name: "John"}), mountNode);

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var html = React.renderComponentToString( HelloMessage({name: "John"})); Server Client {{html}} React.renderComponent( HelloMessage({name: "John"}), mountNode);

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Is the data updated? Only attaches the event handlers

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Performance

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Show lists of 1500 rows Angular: 1.35s ReactJs: 310ms www.williambrownstreet.net/blog/2014/04/faster-angularjs-rendering-angularjs-and-reactjs

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Testing

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var CheckboxWithLabel = React.createClass({ getInitialState: function() { return { isChecked: false }; }, onChange: function() { this.setState({isChecked: !this.state.isChecked}); }, render: function() { return ( {this.state.isChecked ? this.props.labelOn : this.props.labelOff} ); } }); module.exports = CheckboxWithLabel;

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var CheckboxWithLabel = React.createClass({ getInitialState: function() { return { isChecked: false }; }, onChange: function() { this.setState({isChecked: !this.state.isChecked}); }, render: function() { return ( {this.state.isChecked ? this.props.labelOn : this.props.labelOff} ); } }); module.exports = CheckboxWithLabel;

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jest.dontMock('../CheckboxWithLabel.js'); describe('CheckboxWithLabel', function() { it('changes the text after click', function() { var React = require('react/addons'); var CheckboxWithLabel = require('.. /CheckboxWithLabel.js'); var TestUtils = React.addons.TestUtils; var checkbox = TestUtils.renderIntoDocument( ); }); });

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jest.dontMock('../CheckboxWithLabel.js'); describe('CheckboxWithLabel', function() { it('changes the text after click', function() { var React = require('react/addons'); var CheckboxWithLabel = require('.. /CheckboxWithLabel.js'); var TestUtils = React.addons.TestUtils; var checkbox = TestUtils.renderIntoDocument( ); }); });

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jest.dontMock('../CheckboxWithLabel.js'); describe('CheckboxWithLabel', function() { it('changes the text after click', function() { var React = require('react/addons'); var CheckboxWithLabel = require('.. /CheckboxWithLabel.js'); var TestUtils = React.addons.TestUtils; var checkbox = TestUtils.renderIntoDocument( ); }); });

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jest.dontMock('../CheckboxWithLabel.js'); describe('CheckboxWithLabel', function() { it('changes the text after click', function() { var React = require('react/addons'); var CheckboxWithLabel = require('.. /CheckboxWithLabel.js'); var TestUtils = React.addons.TestUtils; var checkbox = TestUtils.renderIntoDocument( ); }); });

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jest.dontMock('../CheckboxWithLabel.js'); describe('CheckboxWithLabel', function() { it('changes the text after click', function() { var React = require('react/addons'); var CheckboxWithLabel = require('.. /CheckboxWithLabel.js'); var TestUtils = React.addons.TestUtils; var checkbox = TestUtils.renderIntoDocument( ); }); });

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// Verify that it's Off by default var label = TestUtils.findRenderedDOMComponentWithTag( checkbox, 'label'); expect( label.getDOMNode().textContent).toEqual('Off'); // Simulate a click and verify that it is now On var input = TestUtils.findRenderedDOMComponentWithTag( checkbox, 'input'); TestUtils.Simulate.change(input); expect( label.getDOMNode().textContent).toEqual('On');

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// Verify that it's Off by default var label = TestUtils.findRenderedDOMComponentWithTag( checkbox, 'label'); expect( label.getDOMNode().textContent).toEqual('Off'); // Simulate a click and verify that it is now On var input = TestUtils.findRenderedDOMComponentWithTag( checkbox, 'input'); TestUtils.Simulate.change(input); expect( label.getDOMNode().textContent).toEqual('On');

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Community

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Who uses?

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umrum.io

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How it's being used at umrum.io

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How it's being used at JusBrasil Newsletter

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@hyetho @helielson Questions?

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References facebook.github.io/react/docs/ www.funnyant.com/reactjs-what-is-it/ youtube.com/watch?v=XxVg_s8xAms youtube.com/watch?v=x7cQ3mrcKaY

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Tools markup.su/highlighter drive.google.com pixlr.com/editor